Wanting to use my Nikon TC-1.4E III teleconverter has been limited to those lens from Nikon that were "compatible". Some folks have modified the TC to allow use with other lenses and such, but I was not just yet ready to grind off the flange tap on this expensive TC that prevents use on "non-compatible" lens.

Recently Lou has done some tests with the PN105 F2.8 which is a highly optimized lens at 1X, and used the modified 1.4TC to extend the PN105 to 1.4X while keeping the PN105 at it's design center of 1X.

Well I haven't got to where I am comfortable grinding off the tap on the TC, so I thought about modifying a cheap eBay Nikon F mount adapter to work with the TC.

I used my Nikon AFS 80-400mm and Nikon 1.4TC mentioned as guides on what needed to be done to allow the F fount to fit to the TC. Many of Nikon lenses will not work with this TC, but many longer modern Nikon lens are compatible, like the AFS 80-400.

Note the 3 locking flange taps sections in the lens, these are located about 120 degrees apart. Also note that the tap near the White lens alignment dot, to the left is split into 2 taps, one is short about 4.4mm with only ~3.7mm separating from the longer length tap. This is where the F mount fits into the TC slot which is 5.2mm wide and without this slot in the lens flange the TC won't allow the lens to mate properly.

With the F mount adapter in hand locate the alignment dot (red in my case) and position it above your compatible lens so you can see where the slot must be cut. Before you mark the slot with a pencil on the adapter align the 2 other taps with the lens taps, in my case this is not having the F mount Red alignment dot aligned with the lens White alignment dot, they differ by quite a few mm!! Once you have the flange taps carefully lined up mark the slot on the adapter flange.

I used a Dremel like tool with diamond bits to carefully grind off this slot as shown. It mounted onto the TC the first time and even "felt" like a proper fit.

Now I just need to flock the rear of the adapter and I can use my 1.4TC

If someone has lots of lenses which they want to use with the TC, though, it is probably better to just remove the offending tab on the TC mount. This would be risk-free if the mount can be unscrewed properly. Unfortunately for me, one of the screws on my TC mount had gotten its head stripped, so I couldn't take it off to grind the tab. So I had no choice but to remove the tab while still mounted on the TC, with a big clumsy drill bit, and that was very messy and very risky for the TC's glass (and I shed some blood too). But it did work.

One day when I get enough courage I'll give the teleconverter a try like you, but this mod should hold for awhile. Hope to soon check out the PN105 & 1.4TC @ 1.4X as you had shown.

I would think the PN105 could be pulled away from 1X a little so with the 1.4TC you might get close to 1.9X. Mark's site indicates the sharpness and resolution hold up well and only the corner drop off above 0.3% at > 1.3X. This should give good coverage on a big 15~20mm chip I would think.

I think you are probably right. I look forward to your tests. The PN105A is such a good lens that it is worth working hard to see how far it can be extended. Such complete freedom from color aberrations is liberating, and it would be nice to have that pleasure at >1.4x._________________Lou Jost
www.ecomingafoundation.wordpress.comwww.loujost.com

Yes it seems to work well with the Nikon TC 1.4 III. Here's a link to the other PN105 image @ 1X without the TC (D850), so can compare. Makes you wonder how well the this might work at 1.7X or 2X with the proper TC, rather than "pulling" the PN105 too far away from 1X which Mark's CP site indicates might not be a good idea.

Sorry if this is a bit off topic but I was ready to ask why someone would use a T/C with printing nikkor.

Then I decided to do the math by myself:

Printing nikkor has a f number of 2.8
This equals to a NA of 0.0.089
I used the following formula:
NA=M/Sqrt(4*f^2*(M+1)^2+M^2) where M=magnification=1 and f=2.8(the f number of printing nikkor)
Resolution in micro meters is derived from the following formula:

R=0.61*(l/NA). for l=550nm and NA=0.089 we get a theoretical resolution of 3.77um

From nyquist theorem a conservative requirement for sensors pixel dimensions is 3.77um/2=1.86um
Finally a FF sensor with pixel size of 1.86um has aprox 19150x12765= 250 million pixel.
Providing that printing nikkor is diffraction limited (which I believe it is) you will need at least a 250mp FF sensor to capture all information.This also means that printing nikkor will out resolve any existing FF sensor so using a TC makes sense.
Hope Rik or some other forum member can verify my calculations.

Last edited by harisA on Mon Nov 27, 2017 11:44 am; edited 1 time in total

Also I assume you are referring to green wavelength which is ~0.55um, not 550um, which should actually be 550nm.

So the resolution predicted by the Rayleigh Criterion is ~1.88um!

Best,

Mike

From WiKi.

"The approximation holds when the numerical aperture is small, but it turns out that for well-corrected optical systems such as camera lenses, a more detailed analysis shows that N is almost exactly equal to
1/2NAi even at large numerical apertures. As Rudolf Kingslake explains, "It is a common error to suppose that the ratio [D/2f] is actually equal to tan ?, and not sin ? ... The tangent would, of course, be correct if the principal planes were really plane. However, the complete theory of the Abbe sine condition shows that if a lens is corrected for coma and spherical aberration, as all good photographic objectives must be, the second principal plane becomes a portion of a sphere of radius f centered about the focal point".[4] In this sense, the traditional thin-lens definition and illustration of f-number is misleading, and defining it in terms of numerical aperture may be more meaningful"

Yes it seems to work well with the Nikon TC 1.4 III. Here's a link to the other PN105 image @ 1X without the TC (D850), so can compare. Makes you wonder how well the this might work at 1.7X or 2X with the proper TC, rather than "pulling" the PN105 too far away from 1X which Mark's CP site indicates might not be a good idea.

Another thing I noted is the corners seem to be a little softer with the TC. I suspect this is a consequence of the TC and not the PN105. I would expect the CA, distortion and corner softness to degrade with increased TC magnification.

I went over to Lens Compare and noted the TC does tend to produce these types of effects, so no surprise here.

Also I assume you are referring to green wavelength which is ~0.55um, not 550um, which should actually be 550nm.

So the resolution predicted by the Rayleigh Criterion is ~1.88um!

Best,

Mike

From WiKi.

"The approximation holds when the numerical aperture is small, but it turns out that for well-corrected optical systems such as camera lenses, a more detailed analysis shows that N is almost exactly equal to
1/2NAi even at large numerical apertures. As Rudolf Kingslake explains, "It is a common error to suppose that the ratio [D/2f] is actually equal to tan ?, and not sin ? ... The tangent would, of course, be correct if the principal planes were really plane. However, the complete theory of the Abbe sine condition shows that if a lens is corrected for coma and spherical aberration, as all good photographic objectives must be, the second principal plane becomes a portion of a sphere of radius f centered about the focal point".[4] In this sense, the traditional thin-lens definition and illustration of f-number is misleading, and defining it in terms of numerical aperture may be more meaningful"

Mike I think I don't agree with you.In the following image there is the Wikipedia text you are referring in your message.

Numeric aperture is calculated here for a thin lens always at a distance equal the the focal length of thIS lens.This is not the case with a macro lens which has different NA depending on working distance (because the cone of entrance light gets thinner and longer as working distance increases) .Would you expect for printing nikkor the same resolving power at 0.5x,1x,2x?If no how is possible to have equal NA at different working distances and different magnifications?
I don't say that my formula is correct (found it in some notes of mine with various formulas) but I believe someone with solid knowledge in optics must enlighten us.

I've always used this NA~1/(2*F) for calculating NA, but I'm no optical physicist, more in the semiconductor area than optics. So take lightly

Either way, the PN105 is certainly out resolving any camera I have, so adding higher magnification TC does make sense (read not empty magnification).

My concern will be what I noted to Lou above, that the TC optical imperfections will mask the final results when used with the PN105. At 1.4X the Nikon TC is already showing small signs of CA, barrel distortion and corner softening in the images. I suspect these will grow worse as I increase the TC magnification. With lesser lenses than the PN105 these TC imperfections probably aren't as noticeable because the basic lenses is introducing it's own imperfections that are on their own noticeable.

The formula NA = 1/(2*F) is correct when the symbols are interpreted properly, but therein lies a trap. F must be the effective F-number of the optics, on the same side that NA is being measured. In general it is not the rated F-number of the lens, although it can be under special circumstances such as infinity focus.

In the case of the Printing Nikkor, the lens is rated at f/2.8 based on its aperture diameter and overall focal length.

But when used as designed, at 1:1, its effective F-number is around f/5.6 at both the subject and the sensor.

Then a simple calculation of NA = 1/(2*5.6) = 0.089, the same number that harisA gets.

Quote:

I used the following formula:
NA=M/Sqrt(4*f^2*(M+1)^2+M^2) where M=magnification=1 and f=2.8(the f number of printing nikkor)

Working from first principles, the formula that I get is much simpler: NA = M/(2*F*(M+1)).

I don't recognize the formula that harisA gives. I also can't figure out how to derive it, so I don't know what assumptions it makes. But for practical purposes both formulas generate very close to the same numbers, only about 0.4% different for the PN.